Generally, fine pattern formation is carried out by photolithography in the manufacture of a semiconductor device. A number of substrates called transfer masks are normally used for such fine pattern formation. The transfer mask comprises generally a transparent glass substrate having thereon a fine pattern made of a metal thin film or the like. The photolithography is used also in the manufacture of the transfer mask.
In the manufacture of a transfer mask by photolithography, use is made of a mask blank having a thin film (e.g. a light-shielding film) for forming a transfer pattern (mask pattern) on a transparent substrate such as a glass substrate. The manufacture of the transfer mask using the mask blank comprises an exposure process of writing a required pattern on a resist film formed on the mask blank, a developing process of developing the resist film to form a resist pattern in accordance with the written pattern, an etching process of etching the thin film along the resist pattern, and a process of stripping and removing the remaining resist pattern. In the developing process, a developer is supplied after writing (exposing) the required pattern on the resist film formed on the mask blank to dissolve a portion of the resist film soluble in the developer, thereby forming the resist pattern. In the etching process, using the resist pattern as a mask, an exposed portion of the thin film, where the resist pattern is not formed, is dissolved by dry etching or wet etching, thereby forming a required mask pattern on the transparent substrate. In this manner, the transfer mask is produced.
For miniaturization of a pattern of a semiconductor device, it is necessary to shorten the wavelength of exposure light for use in photolithography in addition to miniaturization of the mask pattern of the transfer mask. In recent years, the wavelength of exposure light for use in the manufacture of a semiconductor device has been shortened from KrF excimer laser light (wavelength: 248 nm) to ArF excimer laser light (wavelength: 193 nm).
As the transfer mask, there has conventionally been known a binary mask having a light-shielding film pattern made of a chromium-based material on a transparent substrate.
In recent years, there has also appeared a binary mask for ArF excimer laser light using a material (MoSi-based material) containing a molybdenum silicide compound as a light-shielding film. This MoSi-based material may be used as a material of a front-surface antireflection layer formed on a light-shielding layer in a light-shielding film (JP-A-2006-78825 (Patent Document 1)). Patent Document 1 proposes, as a material of the light-shielding layer of the light-shielding film comprising the antireflection layer and the light-shielding layer, a material which is composed mainly of tantalum in terms of etching selectivity to the antireflection layer.
On the other hand, JP-A-S57-161857 (Patent Document 2) discloses a mask blank having a structure in which a tantalum metal layer and a layer of a mixture of tantalum nitride and tantalum oxide are laminated in this order on a transparent substrate.